Best to download the IPL for your specific engine from the Briggs website and at least look at the drawings.

Saying "B&S V-twin 20hp" is kind of like saying Chevy V8. Which one?
Model & Type#'s let one know WHICH specific engine you have.

Thanks for the advice. It is a model 407677 0229 E1. I downloaded the IPL and will look it over.

Typically, if the oil filter is optional, they'll show an optional sump and/or OF cover plate.

The IPL for your engine shows an OF as "standard"?

I'd say get the nipple and install a filter.
After a few minutes running, the filter should get hot if the oil is circulating.

"Briggs/Kohler type" 3/4" X 16 threads 8-11 PSI Bypass Gasket 2.734"OD X2 .430"ID 0.226" thick
Length" Wix Purolator Hastings Kohler B&S Baldwin MotorCraft AC
2.3" 57035 NA LF503 2805001 492932 B7165 NA NA?
2.7" 51056 L35310 LF302 1205001 492056 B1410 NA PF2210
3.4" 51348 L10241 LF157 5205002 491056 BT223 FL793 PF53
4.8" 51516 L20195 LF134 NA NA B243 FL400A PFL400A

It shows the 2.3" long filter. IF you have room, you can use one of the longer ones. Might be cheaper too.

Many thanks for the info! I remember when I bought it that some engines were shipped with filters and some weren't. Never did understand that. I'll get the nipple and add the filter next time I change the oil. This has been an excellent engine and is going strong today. I have about 2 acres to cut so it does get in some time on the lawn!

Let us know how it works out!